Method and apparatus for producing tapered leaf springs



Jan. 20, 1970 J. s. IZETT 3,490,261

METHOD AND APPARATUS FOR PRODUCING TAPERED LEAF SPRINGS Filed April 5.196'? TRANSFER UNIT 2y 1*? RESISTANCE HEATERS DESC DOUBLE COLUMN HAINCONVEYOR ROLLER United States Patent 3,490,261 METHOD AND APPARATUS FORPRODUCING TAPERED LEAF SPRINGS John S. Izett, Grand Blanc, Mich.,assignor to General Motors Corporation, Detroit, Mich., a corporation ofDelaware Filed Apr. 3, 1967, Ser. No. 627,925

Int. Cl. B21b 1/12 US. Cl. 72-207 7 Claims ABSTRACT OF THE DISCLOSUREFor repetitive production of leaf springs tapered from the center bothlaterally and longitudinally, a heated rectangular billet is disposed ona fixture having a flat lower surface and a profiled upper surface. Thefixture is passed linearly along a roller track defining a plane tangentto the lower roll of a double column rolling mill. As the fixture andbillet proceed between the rolls, the upper roll causes the material ofthe billet to be displaced both longitudinally and laterally. Thislongitudinal and lateral flow of metal cooperates with the predeterminedprofile of the fixture to produce a symmetrical bi-tapered leaf spring.

Tapered leaf springs are well known in the prior art. Presently ingeneral use are two principal typesfirst, those wherein the springtapers in thickness from the center toward each end but has a constantwidth from end to end, and second, the so-called bi-tapered leaf springwherein center to end tapering occurs in conjunction with gradualincrease in width from the center toward each end. The present processand apparatus are concerned with production of the latter type.

In the past, the so-called bi-tapered leaf spring has been manufacturedin large quantities by a mill rolling process in which bar stock is fedcontinuously through a double column rolling mill wherein one of therolls is monted eccentric to its axis of rotation. The effect of thiseccentric roll is to provide a strip of recurrent undulation which whenout off at the proper locations produces the desired symmetrical taperedleaf spring configuration. Although satisfactory in manufacturing ofbi-tapered leaf springs of a single size, this process presents certaindisadvantages where short runs of a relatively large number of differentsize leaves are required, since the set-up must be shut down forinstallation and adjustment of a different eccentric roll whenever achange of size of spring is required. This need for equipment change notonly involves considerable down-time, but also limits production to asingle size of spring while the equipment is in operation.

An object of the present invention is to provide apparatus andprocessing techniques permitting repetitive manufacture of either asingle size of bi-tapered leaf spring or repetitive manufacture ofrandom sizes of tapered leaf springs without significant discontinuityof operation of the equipment, or down-time.

The foregoing and other objects, advantages and features of theinvention will become more readily apparent as reference is had to theaccompanying specification and drawing wherein:

FIGURE 1 is a schematic view of a manufacturing installationincorporating apparatus in accordance with the invention;

FIGURE 2 is a side elevation view of a profiled fixture utilized inconjunction with the inventon and showing the initial position of thebillet;

FIGURE 3 is a view similar to FIGURE 2 showing the position of thebillet and tapered fixture at an intermediate stage of manufacture;

FIGURE 4 is a View similar to FIGURES 2 and 3 showing the spring inrelation to the fixture upon completiOn of the operation;

FIGURE 5 is a plan vie-w looking in the direction of arrows 55 of FIGURE4; and

FIGURE 6 is a sectional end elevation looking in the direction of arrows6--6 of FIGURE 4.

Referring now to the drawing and particularly FIG- URE 1, there is shownan arrangement of manufacturing apparatus wherein the numerals 2, 4 and6 designate pairs of resistance heaters arranged in opposed relation toa chain conveyor 8. These heaters elevate the temperature of rectangularbillet 10 to approximately 2100 F. in approximately one minute. Theheating cycle for each heater is staggered in 10 second intervals tothat a fully heated billet is deposited on the chain conveyor every 10seconds. The chain conveyor passes the heated billet through a highpressure water descaler unit 12 to a loading station 14. From loadingstation 14, each billet is placed on an adjacent floating fixture 16. Aplurality of such fixtures are disposed at spaced intervals around atransfer unit 18 disposed in a generally racetrack fashion relative to adouble column rolling mill 20. Thus, as the fixture 16 at the loadingstation progresses linearly between the rolls of the double columnrolling mill, the clockwise preceding fixture moves into the loadingposition and each of the other fixtures in turn progresses one stationforwardly in counterclockwise fashion about the racetrack patternprovided by transfer unit 18. Each sequence or cycle of the fixtures istimed to correspond to the 10 second interval at which heated billetspass through the descaler 12.

In order to utilize the manufacturing apparatus illustrated in FIGURE 1to produce bi-tapered leaf springs in accordance with the invention,each fixture 16 has secured on the upper surface thereof a profiledinsert 22. As shown in FIGURE 2, the upper surface of insert 22 isformed with oppositely vertically inclined faces 24 and 26 which proceedlongitudinally outwardly from the center 28 thereof. Inclined faces 24and 26 of insert 22 are planar in transverse section and thus totallylaterally unconfining with respect to the billet 10. At the loadingstation, the billet 10 is disposed on the upper surface of insert 22 inthe position shown in FIGURE 2 with a major portion of the entire length(approximately /s) of the billet disposed on the right-hand or leadingend of the insert. A pair of lateral guides 30 and 32 shown best inFIGURE 6 are secured on the sides of insert 22 at the midportion thereoffor the purpose of obtaining linear alignment of the billet with theworking face of the insert. After placement of the billet 10 in theposition shown in FIGURE 2, fixture 16 is traversed linearly along theroller track 34 of transfer unit 18 which forms a guiding plane tangentto the upper extremity of the lower roll 36 of the double column mill20. Approximately simultaneously with initial engagement of fixture 16with lower roll 36, upper roll 38 engages the leading end 40 of billet10. Thereafter, progress of the fixture and billet through rolls 36 and38 results from frictional driving engagement produced by the poweredoperation of the rolls. As will be evident from FIGURE 2, initialplastic flow displacement of billet 10 is relatively great since thefinal thickness of the spring is minimal at its opposite ends. As thefixture proceeds forwardly, dislacement of billet material progressivelydecreases as the fixture reaches the midpoint shown in FIGURE 3 and thenprogressively builds up again as the terminal end 42 of the billetleaves the double column roller. After ejection from the rolling mill,the fixture and completed spring blank are transferred laterally towarda trimming station 44 where the spring blank is removed and the emptyfixture continues to follow the sequencing pattern previously described.

Although the inserts 22, as previously mentioned, are profiled only inside elevation thus allowing the billet material unconfined transverseplastic flow when subjected to pressure by the upper roll, the resultingspring leaf exhibits a high degree of both lateral and longitudinalsymmetry of taper. Additionally, linearity or absence of snaking hasbeen found to be well within normal manufacturing tolerances thusrequiring minimal straightening operations, which to the extentnecessary are performed simultaneously with the trimming operation attrimming station 44.

of most significance in the present invention is the fact that a changefrom one shape or size of bi-tapered leaf spring to another may beaccomplished with virtually no down-time since all that is required isthe substitution of differently dimensioned and contoured inserts 22.Since the inserts 22 are permanently mounted on fixtures 16, which inturn are arranged in floating engagement on transfer unit 18, the timerequired to make such a change is minimal. Furthermore, the presentapparatus and process permits, if desired, production in random sequenceof more than one size and shape of spring by mixing the form of insertmounted on each of the sequencing fixtures. Under these circumstances,production of different sizes of springs may be attained on a continuousoperational basis.

While but one embodiment of the invention has been shown and described,it will be apparent that other changes and modifications may be madetherein. It is, therefore, to be understood that it is not intended tolimit the invention to the embodiment shown, but only by the scope ofthe claims which follow.

I claim:

1. Apparatus for manufacture of bi-tapered leaf springs from heatedrectangular billets comprising, a pair of powered rollers mounted forconcentric rotation about parallel horizontally extending verticallyspaced axes, a linear feed mechanism extending in a plane tangent to thesurface of revolution of one of said rollers, a plurality of fixturescarried by said feed mechanism, and

inclined from the center in longitudinal elevation and flat intransverse elevation, said upper surface being located at a level abovesaid tangent plane such that the billet material is displaced bothlaterally and longitudinally as the fixture and insert pass linearlybetween said rollers to simultaneously form both tapers in saidbi-tapered leaf springs during each pass through said pair of poweredrollers.

2. The apparatus of claim 1 including laterally opposed guide meansmounted on said billet support longitudinally midway thereof forinitially aligning said billet on said support.

3. The apparatus of claim 1 wherein said fixtures are arranged in spacedrelation on a sequencing transfer mechanism cooperating with said linearfeed mechamsm.

4. The apparatus of claim 3 wherein said inserts are identicallyprofiled and levelled.

5. The apparatus of claim 3 wherein said inserts are non-uniformly.profiled and levelled whereby springs of different dimension andconfiguration are produced on a continuous repetitive basis.

6. The method of making a bi-tapered leaf spring which comprises thesteps of, heating a rectangular billet to approximately 2100 F.,descaling the heated billet, placing the descaled billet on a billetsupport having a longitudinally oppositely inclined laterally unconfinedupper surface, linearly passing the support and billet into engagementwith a powered double column roller at a level whereby one of saidrollers displaces the billet into conformity with the longitudinalopposite inclination of said surface while simultaneously inducinglateral and longitudinal displacement of the billet material to producesymmetrical tapering of the spring in plan view.

7. The method of claim 6 wherein said billet is initially placed on saidbillet supporting surface with approximately two-thirds of its lengthoverlying the leading half of said surface.

References Cited UNITED STATES PATENTS 149,544 4/ 1874- Tay 72207950,036 2/1910 York 72207 3,345,727 10/ 1967 Komarnitsky 72-207 MILTONS. MEHR, Primary Examiner US. Cl. X.R.

